USART interrupt not working

[mike3]

Posted on October 13, 2003 at 10:57

USART interrupt not working

[mike3]

Posted on May 17, 2011 at 11:55

Hey,

I have Serial Port 0 working fine (receiving and transmitting), but now I want to use an interrupt triggered routing for receiving data.

I can't get the program to run the correct ISR to clear the RI bit.

Here's my code to set up the interrupt:

PS = 1; /* set high priority for USART */

ES = 1; /* enable USART 0 interrupt */

EA = 1; /* enable interrupts */

Here's my code for the ISR routine:

static void USART_isr (void) interrupt SIO_VECTOR using 2

{

unsigned char temp;

if (RI) //If Receive buffer is full

{

temp = (SBUF); //Retrieve Buffer

RI = 0; //set RI bit to 0

}

}

very simple code, but can't seem to get it go to the ISR.

Any suggestions, comments??

Thanks,

Mike

[mike3]

Posted on May 17, 2011 at 11:55

Thanks, for the reply

Interrupt initialization:

void Interrupt_init (void)

{

EA = 0; /* disable interrupts */

timer0_tick = 0;

TR0 = 0; /* stop timer 0 */

TMOD &= 0xF0; /* clear timer 0 mode bits - bottom 4 bits */

TMOD |= 0x01; /* put timer 0 into 16-bit no prescale */

// Calculate timer tollover based on FREQ_OSC to be 10ms periods

timer0_value = 0x10000 - ( ((FREQ_OSC * 5L) / 6L) - 17L);

TL0 = (timer0_value & 0x00FF);

TH0 = (timer0_value >>

;

PT0 = 1; /* set high priority for timer 0 */

ET0 = 1; /* enable timer 0 interrupt */

TR0 = 1; /* start timer 0 */

PS = 1; /* set high priority for USART */

ES = 1; /* enable USART 0 interrupt */

EA = 1; /* enable interrupts */

}

No interrup is being generated on transmit. I only want an interrupt to be generated on receive.

void Serial_Transmit(unsigned char value)

{

unsigned int clock_buf;

//Disable Interrupts

EA = 0;

//Enable RTS signal

P4_3 = TRUE;

SBUF = value; // Xmit the Char

while (TI == 0); // Wait Loop till finished xmit of last char

TI = 0; //set TI bit to 0

//extend the RTS signal to include the stop bit

for (clock_buf=0; clock_buf

{

clock_buf++;

}

//Disable RTS signal

P4_3 = FALSE;

//Enable Interrupts

EA = 1;

}

[mike3]

Posted on May 17, 2011 at 11:55

Oh, sorry,

SCON is set to 0x50

Serial receive and trasmit works perfect, if I disable the interrupts.

Timer 2 is used for baud rate generation, buad rate is perfect at 19200.

Timer 0 is used for something else, and also calls interrupts.

I'm having a hard time with this one.

If I manually clear the RI bit, I'm fine, but I need it to generate an interrupt on receive and go to the ISR so I can clear the RI bit that way.

[jdaniel]

Posted on May 17, 2011 at 11:55

Viper21,

This is a crazy idea, but I don't see anything wrong with your code. The only thing I don't see is the #define for SIO_VECTOR. If you're using Keil C and the first USART, this should be defined as 4. Otherwise, you might be setting up an ISR for the other USART.

Best Regards,

Phaze